System for converting fuel and air into reformate

ABSTRACT

The invention relates to a system for converting fuel and air into reformate with a reformer which has a reaction space, a nozzle for supplying a fuel/air mixture to the reaction space, and a fuel feed for supplying fuel to the nozzle. In the invention, the air inlet area of the nozzle is provided with air guidance means which impart a swirl to the in-flowing air.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a system for converting fuel and air intoreformate with a reformer which has a reaction space, a nozzle forsupplying a fuel/air mixture to the reaction space, and a fuel feed forsupplying fuel to the nozzle. The invention furthermore relates to aprocess for installing one such system.

2. Description of Related Art

Generic systems are used to convert chemical energy into electricalenergy. For this purpose fuel and air, preferably in the form of afuel/air mixture, are supplied to the reformer. In the reformer, theconversion of the fuel with atmospheric oxygen takes place, preferablyvia a process of partial oxidation.

The reformate which has been produced according to the invention issupplied to a fuel cell or a stack of fuel cells, with electrical energybeing released by the controlled reaction of hydrogen, as a component ofthe reformate, and oxygen.

The reformer, as already mentioned, can be designed such that theprocess of partial oxidation is carried out to produce the reformate. Inthis situation, when using diesel as the fuel it is particularlybeneficial to carry out prior reactions before the partial oxidation.Upon using such a process, long-chain diesel molecules can be convertedinto short-chain molecules with a “cold flame” which ultimately promotesreformer operation. In general, a gas mixture which is reacted to H₂ andCO is supplied to the reaction zone of the reformer. Another componentof the reformate is N₂ from the air, and depending on the air ratio andthe temperature, optionally CO₂, H₂O and CH₄ can also be included. Innormal operation, the fuel mass flow is controlled according to therequired output, and the air mass flow is adjusted to an air ratio inthe range of λ=0.4. The reforming reaction can be monitored by differentsensors, for example, temperature sensors and gas sensors.

In addition to the process of partial oxidation, it is likewise possibleto carry out auto-thermal reforming. The process of partial oxidation,in contrast to auto-thermal reforming, is caused by the oxygen beingsupplied sub-stoichiometrically. For example, the mixture has an airratio of λ=0.4. Therefore, since partial oxidation is exothermal,unwanted heating of the reformer can occur in a problematical manner.Furthermore, partial oxidation tends to intensify soot formation. Toprevent soot formation, the air ratio λ can be chosen to be smaller.This is achieved by making some of the oxygen, used for oxidation,available by water vapor. Since oxidation with water vapor proceedsendothermally, it is possible to adjust the ratio between the fuel,oxygen and water vapor such that overall heat is neither released norconsumed. The auto-thermal reforming achieved in this way eliminates theproblem of soot formation and undesirable overheating the reformer.

Similarly, it is possible for further steps of gas treatment to proceedfollowing oxidation in the reformer, and, in particular, methanizationcan be conducted downstream of partial oxidation.

A current fuel cell system is a PEM system (“proton exchange membrane”)which can typically be operated at operating temperatures between roomtemperature and roughly 100° C. Based on the low operating temperatures,this type of fuel cell is often used for mobile applications, forexample in motor vehicles.

Furthermore, high temperature fuel cells are known as SOFC systems(“solid oxide fuel cell”). These systems work in the temperature regionof roughly 800° C. with a solid electrolyte (“solid oxide”) being ableto take over the transport of oxygen ions. The advantage of the hightemperature fuel cells over PEM systems is especially in regard todurability relative to mechanical and chemical loads.

Applications for fuel cells can be in conjunction with generic systemswhich include not only stationary applications, but also applications inthe motor vehicle domain, for example as “auxiliary power units” (APU).

For reliable operation of the reformer, it is important to supply thefuel or fuel/air mixture in a suitable manner to the reaction space ofthe reformer. For example, good mixing of the fuel and air and a gooddistribution of the fuel/air mixture in the reaction space of thereformer are advantageous for the operation of the reformer. Within theframework of this disclosure, a fuel-air mixture can include substancesadded or to be added to the reaction space of the reformer. The addedsubstances are not limited, however, to the mixture of fuel and air, butinstead other substances can be added, for example water vapor in thecase of auto-thermal reforming. To this extent, the concept of fuel/airmixture should be understood in this more general form.

SUMMARY OF THE INVENTION

The object of the invention is to provide a system for the reaction offuel and air into reformate which has advantageous properties withrespect to the introduction of the fuel/air mixture into the reactionspace of the reformer.

The invention is based on the general concept in which an air guidancemeans is provided in the air inlet area of a reformer which imparts aswirl to the in-flowing air. Within the framework of this disclosure theconcept of air inlet area should be understood very broadly. On the onehand, for example, a cylindrical part of the flow path can be a Venturinozzle, but the area outside the Venturi nozzle can also be the airinlet area. What is intended in this disclosure must be understood inthis context. By swirling the air entering the nozzle, i.e., in the airentry area, the atomization quality and thus the function of thereformer can be improved. The reason for this is that the air speed isincreased due to the pronounced tangential motion component of the air.

An embodiment of the invention which is particularly effective is theprovision of an air guidance means which includes an air-guiding devicewith swirl blades. Such an air-guiding device, as a separate component,can be produced independently of the nozzle and seated on the nozzle.

In this embodiment, the swirl blades are located on a carrier mounted onthe nozzle assembly, and two swirl blades together are positioned on thecarrier and with the nozzle assembly form a conical channel. Thetangential air portion and thus the nozzle air swirl can be setdepending on the angular position of these swirl blades to a radialplane. The swirl blades can be located roughly radially or tilted to theradius, and/or the swirl blades can be made flat or curved in the flowdirection.

In another embodiment, the air-guiding device can be a pot-shaped sleevewhich is attached to the nozzle assembly and can have axial air holesformed in the sleeve and peripheral air holes formed in the peripheralwall of the sleeve. By this construction, it is possible to impart adefined swirl to the air flowing into the nozzle.

In this embodiment, the peripheral air openings can be holes which areformed nearly tangentially to the peripheral wall. The tangentialarrangement of the holes makes it possible to impart a swirl to the airwithout further mechanical aids.

Furthermore, the sleeve can also be provided at the peripheral airopenings with air guide blades. It is therefore, unnecessary to directlyimpart the swirl through the peripheral air holes. Rather it is withinthe scope of the present invention to permit the air to flow in throughperipheral air holes in any manner and then to impart the swirl by airguide blades.

Additionally, the system of the invention can also include as part ofthe nozzle a Venturi nozzle with an air inlet area and a diffuser areawhich extends downstream with respect to the air inlet area. One suchVenturi nozzle causes a high axial air pressure gradient so thatcombustion air can be taken in and mixed with fuel in the diffuser area.In the air inlet area or in the area in which the fuel is supplied tothe nozzle, the air flowing into the nozzle has a high speed and anaccordingly low pressure. The high flow velocity of the air promotesabsorption of the fuel by the in-flowing air. As the fuel/air mixturesubsequently flows through the diffuser area of the Venturi nozzle, apressure recovery occurs so that the mixture can flow into thecombustion space of the reformer with sufficient pressure. Furthermore,in the diffuser area advantageous mixing of fuel and air takes place.Thus an effective and economical process is created for delivering thefuel/air mixture into the reformer. The installation cost and productioncosts can be optimized by the choice of different embodiments. Forexample, it is possible to form at least part of the diffuser area in asingle piece with the reformer or the reformer housing or the housing ofthe reaction space, but it is also within the scope of the presentinvention to make and use the nozzle as a wholly independent structurefrom the reformer.

In another embodiment of the invention, the diffuser can be providedwith an opening angle which is variable. However, even when, in thesimplest case, the diffuser area has a uniform opening angle, thestructure can be useful for linking the diffuser part to the reactionspace to provide a larger opening angle in the entry area into thecombustion chamber. This supports the uniform distribution of thefuel/air mixture in the reaction space; while the opening angle of thepart of the diffuser area which is further upstream can be optimizedwith respect to the flow behavior in that area.

Another particularly advantageous embodiment of the system invention isby supplying the liquid fuel to the Venturi nozzle in the vicinity ofthe air inlet area through a needle. This fuel needle is supplied withfuel via a fuel line. Based on the high flow velocity of the in-flowingair, the fuel emerging from the fuel needle is almost unpressurized andis pulled into filaments which then break down into droplets. The highair speeds which are necessary for good atomization in the air inletarea can be achieved as a result of the pressure recovery in thediffuser.

Similarly, still another embodiment of the invention can include asystem in which the fuel feed includes a pipe and a binary fuel nozzlefor supplying the fuel/air mixture to the Venturi nozzle. Therefore,before the fuel enters the Venturi nozzle mixing of the fuel with theair is already taking place which can provide for reliable mixing.

In this embodiment, the fuel feed can be provided as a binary nozzlewhich is another Venturi nozzle. That is, within the Venturi nozzle,which is used within the framework of the invention and which can alsobe called a Venturi tube, there is a smaller Venturi nozzle with a fuelneedle located in the smaller Venturi nozzle. In the smaller Venturinozzle, emergence of the fuel from the fuel needle and premixing takeplace immediately, and the fuel/air mixture then enters the Venturitube, i.e. the Venturi nozzle, of the invention, and is further mixedthere before finally entering the reaction space.

In a particularly preferred embodiment, means are provided such thatsecondary air can flow into the reaction space. The air entering throughthe Venturi nozzle into the reaction space, i.e. the air present in thefuel/air mixture, is called primary air. The secondary air isadvantageously conveyed through secondary air openings in the housing ofthe reaction space. The division of the air into primary air andsecondary air can be useful for preparing a rich, easily ignited mixtureat the outlet of the nozzle. This is particularly beneficial in thestarting process of the system, since at that point the reformerfunctions as a type of burner.

The above embodiment of the invention is further enhanced when the fuelfeed includes a fuel needle with a ratio of the inside diameter d_(i) tothe outside diameter d_(a) being expressed as the following:0.7≦d _(i) /d _(a)<1.

The fuel needle wall is made extremely thin so that at a given fuelthroughput, i.e. for a given inside diameter, the outside diameter is assmall as possible. This construction ultimately leads to a particularlysmall flow barrier due to the presence of the needle. The abovetolerance range is selected in order that the needle can be producedwithout major difficulty. This embodiment provides a system in which theprinciple underlying this invention can be satisfied, that is, the morethe ratio of the inside diameter to outside diameter of the fuel needleapproaches a value of 1 the less the fuel/air mixture is restrictedthrough the nozzle and provides a small resistance to the combustionair.

Another advantageous embodiment of the invention is provided when theVenturi nozzle is axially symmetrical and the fuel needle is axiallyaligned. The axial alignment of the fuel needle provides for a low flowresistance for the combustion air. However, if the effort is made tointroduce the fuel at a certain angle into the flow area of the Venturinozzle, it is also possible to tilt the fuel needle against the axis ofthe Venturi nozzle. In this latter design, the indicated ratio betweenthe inside diameter and the outside diameter contributes to minimizationof the flow resistance.

For this embodiment, it can be useful for the exit plane of the liquidfuel from the fuel needle to run perpendicularly to the flow directionof the liquid fuel through the fuel needle. In this construction,axially symmetrical emergence of the fuel from the fuel needle resultsignoring gravity.

However, it can also be beneficial for the exit plane of the liquid fuelfrom the fuel needle to run obliquely to the flow direction of theliquid fuel through the fuel needle. In this embodiment, a preferentialdirection upon emergence of the fuel from the fuel needle can beimplemented without the fuel needle tilting overall against the axis ofthe Venturi nozzle. Due to the oblique cut of the fuel needle in theexit area an increase of the flow resistance as a result of the tiltedfuel needle can be avoided, while emergence of the fuel from the fuelneedle, e.g., oriented against the force of gravity, is still possible.

This embodiment can also include an exit opening of the fuel needlewhich is provided with tips and/or is crenellated. This constructionmakes it possible for the fuel to be introduced into the fuel chamberwith a great radial extension which cannot be achieved in an optimummanner in a structure without such an edge feature at the exit due toconstriction effects.

Another embodiment of the invention includes a system in which the airinlet area has an essentially cylindrical part which has a transition tothe diffuser area such that the exit opening of the fuel needle islocated in the cylindrical part and an axial distance exists between theexit opening of the fuel needle and the transition. This ensures thatthe liquid fuel which has emerged from the exit opening of the fuelneedle is still transported along with the in-flowing air over a certaindistance through a region of high flow velocity. This structure providesespecially good atomization. In most cases, it is beneficial to placethe exit from the fuel needle at the start of the cylindrical part ofthe air inlet area of the Venturi nozzle such that essentially theentire cylindrical area is available for good distribution of theatomized fuel in the rapidly flowing combustion air.

Additionally, another embodiment of the invention includes at least oneinstallation of the reformer in a motor vehicle wherein the opening ofthe fuel needle is located above the axis of the Venturi nozzle. Thisembodiment makes it possible to arrange the fuel needle parallel to theaxis of the Venturi nozzle and at the same time counteract the effect ofgravity. If the installation position of the fuel needle is chosen withrespect to the axis of the Venturi nozzle to be positioned relative tothe reformer such that it is radially offset upward from the axis andthen in the peripheral direction, two installation positions of thereformer can be provided. Each of the two installation positions providefavorable equalization of the force of gravity by the location of theopening above the axis of the Venturi nozzle.

The embodiments of the invention can further include a nozzle composedof ceramic material and can include the air guidance means being made ina single piece with the nozzle. In this construction, a nozzle can beeconomically produced. That is, the ceramic material can be easilymachined, and numerous shaping variations are also possible. Inparticular, the air guidance means which imparts a swirl to the airoutside the air inlet area can be constructed in a single piece with thenozzle. As an additional advantage of using a ceramic, the area of thenozzle in which the fuel needle is located is not subjected to overlyhigh temperatures such that ignition of the of fuel emerging form thenozzle does not occur. The one-piece execution of the air guidance meansmakes it possible to easily adhere to tolerances since miscalibration ofthe air guidance means is no longer a factor when the reformer isassembled.

Still another advantageous embodiment of the invention includes a systemwhere the nozzle has means for holding a glow pin. The positioning ofthe glow pin with respect to the nozzle is an important parameter withrespect to good starting behavior of the reformer. In heaters of theprior art, the glow pin was generally held by the reformer housing suchthat positioning fluctuations occur with respect to the nozzle. Thesetolerance problems can be eliminated by a nozzle that includes means forholding the glow pin. The glow pin always has the same position relativeto the nozzle.

In this embodiment, the nozzle of the invention is provided with atleast a partial cylindrical shape and is provided with air guidancemeans which forms channels offset with respect to the radial direction.The air flowing perpendicular to the axis of the nozzle is therefore notonly radially supplied, but is provided at an offset. This offsetdetermines the swirl imparted to the air, and thus determines the flowbehavior and ultimately the quality of the combustion.

In a preferred embodiment, the air guidance means is constructed to haveessentially triangular base surfaces with the corners being rounded. Inthis embodiment, the channel offset can be easily implemented. Therounding of the corners is also advantageous for uniform flow behavior.

In another preferred embodiment of this invention, the means for holdingthe glow pin is a hole which is slanted relative to the cylinder axis.The glow pin can then be simply introduced into the hole for suitablepositioning. A stop on the glow pin and/or within the hole enables theglow pin to be guided into its optimum position with respect to thenozzle.

The nozzle of the invention can further include an at least essentiallycylindrical part of the nozzle having an essentially cylindricalshoulder with an enlarged diameter and can include, as a means ofholding the glow pin, a hole which penetrates the shoulder and which isslanted relative to the cylinder axis. In this embodiment, the glow pincan be held in the area such that it influences, as little as possible,the flow behavior of the in-flowing fuel-air mixture. With a cylindricalshoulder having a larger diameter than the remaining nozzle body, thisfeature can be easily implemented.

In a variation of this embodiment, the at least essentially cylindricalpart of the nozzle has an essentially cylindrical shoulder with anenlarged diameter and the cylindrical shoulder has recesses for theholding of mounting pins. These mounting pins can be permanently mountedon the heat shield of the reformer. The relative positioning of thenozzle is fixed in this embodiment by recesses in the shoulder and theposition of the mounting pins. Thus mounting is easily achieved withprecise tolerances.

In another preferred embodiment, the system of the invention can includea structure in which the reformer, the nozzle and the fuel feed arelocated on a single axis, and that means are provided for holding thenozzle and the fuel feed, such as via at least two axially alignedmounting pins mounted on the reformer. Additionally, the nozzle and thefuel feed can include positioning means which interact with the mountingpins such that the means for holding the components interact with themounting pins, and the reformer, the nozzle, the fuel feed and the meansfor holding the components are successively axially positioned. In thisembodiment, all positions of the components are oriented relative to themounting pins so that precise tolerances can be maintained. The fuelneedle is also positioned very accurately with respect to the nozzle.Furthermore, the positioning of the glow pin, required for starting, isdictated by the positions of the mounting pins. As a result, a stablestructure is achieved which ensures reformer operation with greatefficiency.

Another embodiment of the invention includes a system in which the meansfor holding the components includes a spring which is held on themounting pin by clamp disks. Attachment with one such spring has theadvantage that mechanical stresses, especially as a result oftemperature effects, can be equalized. In systems of the prior art,undesirably high forces can act on the reformer and on an optional heatshield of the reformer due these mechanical stresses, which can resultin deformation of the reformer.

In still another embodiment of the invention, the mounting pins arewelded onto the reformer. In this embodiment, the mounting pins aresecurely connected to the reformer in a defined position with respect tothe latter.

In still another embodiment of the invention, between the nozzle and thereformer is provided a seal. The seal provides both thermal insulationand for matching of the nozzle to the heat shield of the reformer.

In this embodiment, the seal can be provided with at least one micalayer facing the reformer and at least one graphite layer facing thenozzle. This structure ensure that the advantageous properties of theseal are realized in a reliable manner.

In still another embodiment of the invention, the fuel feed is knittedmetal mesh. This structure breaks down bubbles in the fuel.Additionally, a counter-pressure for a damper, which is optionallylocated on the fuel line, is made available.

Another embodiment of the invention, includes a process for installing asystem for conversion of fuel and air into reformate. The processinclude a system having at least two mounting pins in which a nozzle isguided in the axial direction onto the mounting pins, a fuel feed isguided in the axial direction onto the mounting pins, and a means isprovided for holding the components which are guided in the axialdirection on the mounting pins. This process can be implementedparticularly easily since all components are supplied in the axialdirection. Additionally, the process can be automated such that largenumbers of reformer assemblies can be produced within a short time.

In still another embodiment of the invention, the process can includethe step, before guiding the nozzle onto the mounting pins, of providinga seal which is guided in the axial direction onto the mounting pins. Adevice with a seal can thus be easily integrated into the process sincethe seal is also guided in the axial direction onto the mounting pins.

In still another embodiment of the invention, the assembly processincludes a means for holding the components which is a spring such thatthe spring is guided in a force-controlled manner onto the mountingpins. The spring cooperates with clamp disks which fix the spring in itsassembled position.

With this embodiment, within a single assembly uniform tolerances can beestablished with respect to heat and temperature properties of theassembly. The spring force imparted by the spring ensures that the lossof tolerances, as a result of different heating of the components,different final temperatures of components and different coefficients oftemperature expansion, can be reduced. That is, the tolerances can beequalized.

The present invention is based upon the determination that majoradvantages are realized in the use of a Venturi nozzle to introduce thefuel/air mixture into the reformer. A Venturi nozzle offers theadvantage of the liquid fuel being taken up efficiently in areas of highflow velocity into the in-flowing air. Subsequently, a sufficientpressure build-up is ensured when introducing the fuel/air mixture intothe reformer. A Venturi nozzle can be economically produced in each ofthe numerous embodiments. Furthermore, installation processes for eachof the embodiments of the invention are particularly efficient.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained by way of example with reference to theattached drawings.

FIG. 1 shows a schematic block diagram of a system in which anembodiment of the invention can be used;

FIG. 2 shows a schematic sectional view of one embodiment of theinvention;

FIG. 3 shows a schematic sectional view of another embodiment of theinvention;

FIG. 4 is a diagram which illustrates the axial pressure behavior in theVenturi nozzle;

FIG. 5 shows a schematic sectional view of another embodiment of theinvention;

FIG. 6 shows a perspective of a carrier with an air-guiding device foruse in an embodiment of the invention;

FIG. 7 shows schematic sectional view of another embodiment of theinvention;

FIG. 8 shows a schematic sectional view along the cross sectional planeidentified by A-A in FIG. 7;

FIG. 9 shows a schematic sectional view, corresponding to the section asshown in FIG. 8, of another embodiment of an air-guiding device;

FIG. 10 shows a schematic sectional view of another embodiment of theinvention;

FIG. 11 shows a schematic sectional view along the plane identified byB-B in FIG. 10;

FIG. 12 shows a fuel needle with a first exit opening for use in anyembodiment of the invention;

FIG. 13 shows a fuel needle with a second exit opening for use in anyembodiment of the invention;

FIG. 14 shows a fuel needle with a third exit opening for use in anyembodiment of the invention;

FIG. 15 shows a partially cut side view of a nozzle for use in anyembodiment of the invention;

FIG. 16 shows an overhead view of the air inlet area of a nozzle for usein a system as claimed in the invention; and

FIG. 17 shows a schematic sectional view of another embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic block diagram of a system in which thisinvention can be used. Fuel 216 is supplied to a reformer 214 via a pump240. Furthermore, air 218 is supplied to the reformer 214 via a fan 242.The reformate 220 produced in the reformer 214 travels via a valve means222 to the anode 224 of a fuel cell 212. The cathode 230 of the fuelcell 212 is supplied with cathode feed air 228 via a fan 226. The fuelcell 212 produces electrical energy 210. The anode exhaust gas 234 andthe cathode exhaust air 236 are supplied to the burner 232. Likewise,reformate can be supplied to the burner 232 via the valve means 222. Thethermal energy produced in the burner 232 can be supplied in a heatexchanger 238 to the cathode feed air 228 so that it is preheated.Exhaust gas 250 flows out of the heat exchanger 238.

The system shown in conjunction with the figures described below can beused to supply a fuel/air mixture to the reformer 214.

FIG. 2 shows a schematic sectional view of one embodiment of the systemof the invention. The system comprises a reformer 10 with a reactionspace 12. A Venturi nozzle 14 is connected to the reformer 10. Thenozzle has an air inlet area 18 and a diffuser 20 with a cross sectionwhich increases in the direction to the reformer 10. Within the Venturinozzle 14 in the vicinity of the air inlet area 18 there is a fuel feed16. The fuel feed 16 comprises a pipe 24 for the feed of fuel and abinary nozzle 26. The binary nozzle 26 is provided with an opening 80into which air 82 can flow. The air is mixed within the binary nozzle 26with fuel supplied by the pipe 24. From the downstream opening of thebinary nozzle 26, a fuel/air mixture can emerge which is entrained bythe air 82 which enters the air inlet area 18 of the Venturi nozzle 14.The fuel/air mixture mixes with the air 82 which has flowed into the airinlet area 18 of the Venturi nozzle 14, and the resulting fuel/airmixture travels via the diffuser 20 into the reaction space 12 of thereformer 10. Furthermore, an opening 30 to the reaction space 12 of thereformer 10 can be provided through which secondary air 82 can enter thereaction space 12.

FIG. 3 shows a schematic sectional view of another embodiment of thesystem of the invention. The fuel feed 16 in the system shown in FIG. 3is different from in the system shown in FIG. 2. The fuel is firstsupplied in turn via a pipe 24, but then travels into another Venturinozzle 28 which is much smaller than the Venturi nozzle 14. In theVenturi nozzle 28 the liquid fuel is picked up and atomized by the air82 which is flowing past the exit opening of the pipe 24 at high speed.The resulting fuel/air mixture is then entrained by the air 82 whichflows in the air inlet area 18 of the Venturi nozzle 14 so that it canmix with it.

FIG. 4 is a diagram which illustrates the axial pressure distribution ina Venturi nozzle. The pressure difference Δp between the pressure at acertain coordinate and the pressure in the reaction space 12 (see FIGS.2 and 3) is plotted. The air 82 is generally fed into the air inletregion 18 of the Venturi nozzle 14 by a fan (not shown), this air beingmade available with only a low overpressure. As a result of the speedincrease of the in-flowing air the pressure drops to a minimum value. Asthe air continues to flow through the diffuser of the Venturi nozzle,the flow velocity decreases again and the pressure increases graduallyto the reaction chamber pressure.

FIG. 5 shows a schematic sectional view of another embodiment of asystem of the invention. The system comprises a Venturi nozzle 14 with anozzle assembly 44. Furthermore, there is a fuel feed 72 for supplyingliquid fuel to the nozzle 14. The fuel is supplied to the air inflowarea 92 via the fuel exit 84 of the fuel needle 22, is entrained by thein-flowing air and then travels as a fuel/air mixture to the reactionspace 12 of the reformer 10 via the diffuser 20. The nozzle assembly 44is connected downstream of an air-guiding device 42 which impresses aswirl on the air flowing into the Venturi nozzle 14. The air-guidingdevice 42 is a carrier 46 which is located at a distance opposite theend face 90 of the nozzle assembly 44, and is for example circular. Theair-guiding device 42 forms an annular gap 86 together with the end face90 of the nozzle assembly 44. On the carrier 46 there are swirl blades88 which are pointed against the end face 90 of the nozzle assembly 44and adjoin it in the assembled position.

FIG. 6 shows a perspective view of an air-guiding device 42 for use in asystem of the invention. The swirl blades 88 are arranged offset on acarrier 46 with respect to the radius of the circular arrangement inorder to produce a tangential flow component. Two swirl blades 88cooperate with the carrier 46 and the nozzle assembly 44 form a conicalchannel 48.

FIG. 7 shows a schematic cross sectional view of another embodiment of asystem of the invention. This embodiment of the system of the inventiondiffers from that shown in FIG. 5 in that the air-guiding device 42 ismade as a pot-shaped sleeve 96. The sleeve 96 in its bottom has axialholes 94, and in the peripheral wall 100 of the sleeve 96 tangentialholes 98 are formed. The sleeve 96 is attached to the nozzle assembly ofthe Venturi nozzle 14, for example by slipping it on or by some otherform of positive, non-positive or material connection. The axial holes94 and the tangential holes 98 are matched to one another such that adefined swirl is imparted to the in-flowing air.

FIG. 8 shows a schematic sectional view along the cross sectional planeidentified by A-A in FIG. 7. A sample arrangement of the axial holes 94and the tangential holes 98 in the sleeve 96 is illustrated. By varyingthe number, size and arrangement of openings or holes 94, 98, the swirlof the air flow can be adjusted if desired.

FIG. 9 shows a schematic sectional view, corresponding to FIG. 8, ofanother embodiment of an air-guiding device. The sleeve 96 has in itsperipheral wall 100 air holes 102 which are bounded towards the centerof the sleeve 96 by an air guide blade 104 assigned to each respectiveair opening 102. A tangential flow component is therefore impressed onthe in-flowing air by the air guide blades 104.

FIG. 10 shows a schematic sectional view of another embodiment of asystem of the invention. The function and properties of the componentsshown result from the preceding description with consideration of thereference numbers. The representation is highly schematic so that theimportant components of the system of the invention can be illustrated.In the cylindrical part 38 of the Venturi nozzle 14 there is a fuelneedle 22 for supplying fuel. On the one hand, it is a desirable toarrange the fuel needle 22 in exactly this narrowed cylindrical part 38of the Venturi nozzle 14, since the combustion air 82 flowing with highflow velocity promotes atomization of the fuel. On the other hand, thefuel needle 22 also represents a flow barrier to the in-flowingcombustion air 82. This is a basic problem which is solved by thefeatures described below in conjunction with the system of theinvention. Line B-B identifies a radial cutting plane to which referenceis made in the following description.

FIG. 11 shows a sectional view along the plane identified in FIG. 10with B-B. It can be easily recognized that this invention solves theproblem described in conjunction with FIG. 10. That is, by choosing theratio between the inside diameter d_(i) and the outside diameter d_(a)of the fuel needle 22 to be as near a value of 1 as possible, the fuelneedle 22 represents a minimum flow resistance for the in-flowingcombustion air in the Venturi nozzle 14.

FIG. 12 shows a fuel needle 22 with a first exit opening for use in asystem of the invention. In this embodiment, the exit plane 32 of thefuel 106 from the fuel needle 22 is perpendicular to the main flowdirection of the fuel 106. This results in constriction of the fuel 106outside the fuel needle 22 which can be disadvantageous with respect tothe uniform distribution of the fuel 106 in the Venturi nozzle andultimately in the combustion chamber.

FIG. 13 shows a fuel needle 22 with a second outlet opening for use in asystem of the invention. In this embodiment, the exit opening of thefuel needle 22 has crenelations 36. These crenelations 36 concentrateemerging fuel 106 in certain areas and ultimately the result in the fuel106 being distributed homogeneously over the entire flow cross section.

FIG. 14 shows a fuel needle 22 with a third exit opening for use in asystem of the invention. In this embodiment, the fuel needle 22 isprovided with a beveled opening 34. The beveled opening 34 imparts tothe out-flowing fuel 106 a preferential direction so that for examplethe effect of the force of gravity can be counteracted.

The particular designs of the fuel needles can be combined in any mannerwith any other embodiments of the invention. For example, it is possiblefor a slanted exit plane to be combined with a crenellated structure.

FIG. 15 shows a partially cutaway side view of one embodiment of anozzle 14 for use in a system of the invention. The Venturi nozzle 14 ismade of ceramic material which simplifies the production of the nozzle14 compared to metal nozzles. In the air inlet area 18, there are airguidance means 40 which are constructed in one piece with the nozzle 14.In particular, the air-guidance means 40 are also made of ceramicmaterial. The air guide means 40 are aligned such that a swirl isimparted to the supplied air the details of which are illustrated belowwith reference to FIG. 16. The Venturi nozzle 14 is furthermore providedwith a hole 62. A glow pin 64 can be inserted into this hole 62 and isused to ignite the fuel/air mixture entering the reaction space which isnot shown in FIG. 15. In particular, when the system of the inventionstarts, the reformer works in the manner of a burner so that initialignition of the fuel/air mixture is necessary. It is advantageous in anarrangement of the glow pin 64 in a hole 62 of the nozzle 14 that thepositioning of the glow pin 64 is fixed with respect to the nozzle 14.Therefore, the positioning of the glow pin 64 does not depend on anyother components. In this way, very precise tolerances can be maintainedwith respect to the installation location of the glow pin 64. The hole62 advantageously penetrates the cylindrical shoulder 66 of the nozzle14 with an increased radius which has the advantage that the flowbehavior of the nozzle 14 is influenced only little by the hole 62 or bythe glow pin 64 which is located in the hole 62.

FIG. 16 shows an overhead view of the air inlet area 18 of a nozzle 14for use in the system of the invention. One possible configuration ofthe air inlet area 18 by the air guide elements 40 is shown. The airguide elements 40 form channels 48 for the in-flowing air. Thesechannels 48 have an offset position with respect to the radius of thestructure located essentially on one axis. Air flowing in from theoutside undergoes a swirl which provides for advantageous propertieswith respect to atomization of the fuel emerging from the fuel needle.Furthermore, in this illustration, the arrangement of the opening 62 forholding the glow pin can be seen as well. The glow pin penetrates anessentially cylindrical shoulder 66. Furthermore, the shoulder 66 isprovided with recesses 68 which define the installation position of thenozzle 14 which is detailed below with respect to FIG. 17.

FIG. 17 shows a schematic cross sectional view of another embodiment ofa system of the invention in which the end of the reformer 10 facing thenozzle 14 is shown. The reformer 10 is bordered by the heat shield 108.On this heat shield 108, there are two mounting pins 80 in thisembodiment. The mounting pins 70 can be welded to the heat shield 108 orto the reformer 10. The mounting pins 70 will define the positioning ofthe other components as described below. Initially, a seal 78, whichpreferably includes a mica layer turned toward the reformer 10 and agraphite layer turned toward the nozzle 14, is positioned on themounting pins 70. A ceramic nozzle 14 follows which sits with itsrecesses 88, shown in FIG. 16, on the mounting pins 70. A fuel feed 72,which is connected to the fuel needle 22, is next seated on the nozzle14. This fuel feed 72 is also positioned by the mounting pins 70. Thefuel feed 72 is supplied with fuel by the fuel line 110 in which thefuel sensor 112 is located. The fuel feed 72 is followed by a spring 74which is also seated on the mounting pins 70. The spring 74 is held byclamping disks 76 which sit immovably on the mounting pins 70. Thespring 74 is shown in the tensioned state in which the legs of thespring 74 are parallel to the interposed disks 76. In the released stateof the spring 74 the legs of the spring are bent upward in the directiontoward the interposed disks 76. A glow pin (not shown) is positioned inthis assembly according to the embodiment of a nozzle 14 shown in FIG.15 and is held by a wire spring (not shown) which is supported on thenozzle 14.

By this assembly process, the fuel feed 72 and thus the fuel needle 22are automatically aligned with respect to the nozzle 14. Therefore, onlytwo components are involved which influence the fuel feed and the mixingof the fuel with combustion air so that very small, precise tolerancescan be maintained. This type of installation is made possible by themounting pins 70. Likewise, the glow pin 64 can be positioned exactlywith respect to the nozzle 14 and the reformer 10.

The production of the structure shown in FIG. 17 can be fully automated.In particular, since the installation direction is uniformly axial only“threading” of the parts must be carried out. While the seal 78 enablesthermal insulation, coupling of the nozzle ceramic 14 to the metal ofthe heat shield 108 and tolerance equalization to be achieved. Thesystem of the invention can be advantageously mounted bypower-controlled pressing of the clamp disks 76 onto the mounting pins70 such that, with regard to the heat and temperature properties of thesystem, uniform prerequisites can be established. Furthermore, as aresult of the spring force applied by spring 74, the tolerances as aresult of different heating of the components, different finaltemperatures of the components and different coefficients of temperatureexpansion can be equalized.

1. Device for converting fuel and air into reformate comprising areformer which includes a reaction space, a nozzle for supplying afuel/air mixture to the reaction space, wherein the nozzle is a Venturinozzle having an air inlet area and a diffuser area which extendsdownstream with respect to the air inlet area, and a fuel feed forsupplying fuel to the nozzle, wherein the air inlet area of the nozzleincludes an air guidance means for imparting a swirl to the flow of airinto the nozzle, and wherein the nozzle is composed, at least in part,of a ceramic material, and wherein the nozzle and air guidance means areintegrally formed as a single unit.
 2. A device as claimed in claim 1,wherein the diffuser area of the nozzle includes an opening angle whichis variable.
 3. A device as claimed in claim 1, wherein the fuel feedincludes a fuel needle in which the fuel needle is located in thevicinity of the air inlet area.
 4. A device as claimed in claim 1,wherein the fuel feed includes a pipe and binary nozzle to supply theVenturi nozzle with a fuel/air mixture.
 5. A device as claimed in claim4, wherein the binary nozzle is another Venturi nozzle.
 6. A device asclaimed in claim 1, further comprising a means to feed secondary airinto the reaction space.
 7. A device as claimed in claim 1, wherein thefuel feed includes a fuel needle which is located in the vicinity of theair inlet area, and wherein a ratio of the inside diameter d_(i) to theoutside diameter d_(a) of the fuel needle is in the range0.7≦d_(i)/d_(a)<1.
 8. A device as claimed in claim 3, wherein theVenturi nozzle is axially symmetrical and the fuel needle is axiallyaligned with the Venturi nozzle.
 9. A device as claimed in claim 3,wherein an exit plane of the liquid fuel from the fuel needle isperpendicular to a flow direction of the liquid fuel through the fuelneedle.
 10. A device as claimed in claim 3, wherein an exit plane of theliquid fuel from the fuel needle extends obliquely with respect to aflow direction of the liquid fuel through the fuel needle.
 11. A deviceas claimed in claim 3, wherein the fuel needle includes an outletopening provided with a plurality of tips or crenelations.
 12. A deviceas claimed in claim 1, wherein the air inlet area includes anessentially cylindrical part which has a transition to a diffuser area,and wherein the fuel feed includes a fuel needle having an exit openinglocated in the cylindrical part such that there is an axial distancebetween the exit opening of the fuel needle and the transition.
 13. Adevice as claimed in claim 3, wherein the device is to be installed in amotor vehicle and an exit opening of the fuel needle is located above anaxis of the Venturi nozzle.
 14. A device as claimed in claim 1 whereinthe nozzle further includes a means for holding a glow pin.
 15. A deviceas claimed in claim 1, wherein the nozzle has an at least partiallycylindrical shape and the air guidance means form channels which areoffset with respect to a radius of the nozzle.
 16. A device as claimedin claim 1, wherein the air guidance means has an essentiallytriangularly shaped base surface with the corners of the triangularshaped base surface being rounded.
 17. A device as claimed in claim 14,wherein the means for holding the glow pin is a hole which is slantedwith respect to an axis of the nozzle.
 18. A device as claimed in claim14, wherein the nozzle is at least partially cylindrical and includes acylindrical shoulder having an enlarged external diameter wherein themeans of holding the glow pin comprises a hole which extend though thecylindrical shoulder and is slanted to the cylinder axis of the nozzle.19. A device as claimed in claim 1, further comprising mounting pins forholding the reformer, nozzle and fuel feed in alignment, wherein thenozzle is at least partially cylindrical and includes a cylindricalshoulder having an enlarged external diameter and having a plurality ofrecesses for engaging mounting pins.
 20. A device as claimed in claim19, further comprising a means for holding the nozzle and the fuel feedin an assembled relationship such that the reformer, the nozzle and thefuel feed are located successively on a single axis, wherein there areat least two axially aligned mounting pins which are mounted on thereformer, the nozzle and the fuel feed include positioning means whichinteract with the mounting pins, and the means for holding the nozzleand the fuel feed interact with the mounting pins.
 21. A device asclaimed in claim 20, wherein the means for holding the nozzle and thefuel feed includes a spring which is held on the mounting pins by clampdisks.
 22. A device as claimed in claim 20, wherein the mounting pinsare welded to the reformer.
 23. A device as claimed in claim 1, furthercomprising a seal situated between the nozzle and the reformer.
 24. Adevice as claimed in claim 23, wherein the seal includes at least onemica layer which faces the reformer and at least one graphite layerwhich faces the nozzle.
 25. A device as claimed in claim 1, wherein thefuel feed includes a metal mesh.
 26. A process for assembling a systemfor conversion of fuel and air into reformate including a reformer andat least two mounting pins on the reformer comprising the steps of:guiding a nozzle in an axial direction onto the mounting pins, whereinthe nozzle is a Venturi nozzle having an air inlet area and a diffuserarea, which extends downstream with respect to the air inlet area, andwherein the air inlet area of the nozzle includes an air guidance meansfor imparting a swirl to the flow of air into the nozzle, and whereinthe nozzle is composed, at least in part, of a ceramic material, and thenozzle and air guidance means are integrally formed as a single unit,and guiding a fuel feed in the axial direction onto the mounting pins,and assembling on the mounting pins a means for holding the nozzle andfuel feed in an assembled condition in the axial direction on themounting pins.
 27. The process as claimed in claim 26, wherein prior toguiding the nozzle on the mounting pins a seal is guided in the axialdirection onto the mounting pins.
 28. The process as claimed in claim26, wherein the means for holding includes a spring and clamp disks, andwherein the assembling includes the step of guiding the spring in aforce-controlled manner onto the mounting pins by interaction of clampdisks with the spring.